A synthesis gas is a mixed gas containing hydrogen and carbon monoxide and is widely used as a raw material for the synthesis of ammonia, methanol, acetic acid, etc.
Such a synthesis gas may be produced by reaction of a hydrocarbon with steam and/or carbon dioxide in the presence of a catalyst. In the reaction, however, carbon deposition reactions occur as side reactions to cause carbon deposition which brings about a problem of catalyst poisoning.
The raw materials for the carbon deposition are a carbon-containing organic compound used as a raw material and CO produced in situ. The carbon deposition is accelerated as the partial pressures of these raw materials increase. Therefore, it is possible to reduce the amount of the carbon deposition by increasing the feed amount of steam and carbon dioxide while reducing the reaction pressure. In this case, however, it is necessary to excessively use steam and carbon dioxide in order to reduce the partial pressures of the carbon-containing organic compound and CO, so that several disadvantages are caused. For example, consumption of heat energy required for preheating steam and carbon dioxide increases. Further, costs for the separation of these gases from the product increase. Moreover, since a large reaction apparatus is required, the apparatus costs increase.
JP-A-5-208801 discloses a carbon dioxide-reforming catalyst containing a Group VIII metal supported on high purity, super-fine single crystal magnesium oxide. JP-A-6-279003 discloses a carbon dioxide-reforming catalyst containing a ruthenium compound supported on a carrier composed of a compound of at least one alkaline earth metal oxide and aluminum oxide. JP-A-9-168740 discloses a carbon dioxide-reforming catalyst containing rhodium supported on a carrier formed of a Group II-IV metal oxide or a lanthanoid metal oxide or a composite carrier composed of the above metal oxide and alumina. The reaction experiments using these catalysts are performed under ambient pressure. At a high pressure, which is industrially significant, these catalysts show a high carbon deposition activity and, hence, are not satisfactory as industrially applicable catalysts.
The objects of the present invention are:
(1) to provide a process for the production of a synthesis gas by reaction of a carbon-containing organic compound with steam and/or carbon dioxide, which process can solve a problem of carbon deposition; PA1 (2) to provide a process for the production of a synthesis gas of the above-mentioned type, in which a catalyst having suppressed carbon deposition activity is used. PA1 (i) the electronegativity of the metal ion of the carrier metal oxide is 13.0 or less; PA1 (ii) the catalyst has a specific surface area of 25 m.sup.2 /g or less; and PA1 (iii) the amount of the supported catalytic metal is 0.0005-0.1 mole % based on the carrier metal oxide. Such a catalyst having a considerably suppressed carbon deposition activity has been first found by the present inventors. PA1 Xi: electronegativity of the metal ion PA1 Xo: electronegativity of the metal PA1 i: valence electron number.
Other objects of the present invention will be understood from the following description of the specification.